If it didn't, it would just be the devanagari character र (Ra), which would be incorrect since in devanagari, the currently used symbol for the Rupee is रु (Ru). Now the reason they don't use the current devanagari symbol is because that's not representative of the entire country since there are many official languages, and few of them use the devanagari script.
Ha! So they come up with a symbol which is basically a distorted version of the devanagari one.
Well, really any decision is going to leave them open to criticism like this. Given that Hindi has more speakers in India than any other language, and is not the only language that uses Devanagari I think it's a pretty defensible choice.
The problem is that your suggestion would be interpreted as Hindi-favoritism, when India actually has many languages and scripts.
You're not "Tamilian", you're Tamil.
Both "Tamilian" and "Tamil" are valid nouns for a Tamil person, but "Tamil" is more often used as an adjective or to refer to the Tamil language.
to get = symbol, which stands for equality (among people, religion,etc)
€ and £ both (can) have two lines, the $ sign can have two lines, too. The two lines seem to me to be a allusion to that. (That’s why the € sign has two lines, anyway.)